Pressure responsive switch



Sept. 9,1958 M. KNOBEL PRESSURE RESPONSIVE swrrcu Filed Oct. 15, 1956 H TE N NB mo m m w J X M PRESSURE RESPONSIVE SWITCH Max Knobel, Boston, Mass, assignor to Pratt & Whitney Company, Inc., West Hartford, Conn., a corporation of Delaware Application October 15, 1956, Serial No. 615,928

12 Claims. (Cl. 200-83) This invention relates to a pressure responsive switch, and more specifically to an electrical switch actuated in response to pneumatic signals.

In the art of pneumatic gaging, a frequently encountered problem is that of operating electrical circuits of one kind or another, such as counting and alarm circuits for example, in response to pneumatic signals which are functions of dimensional parameters being measured. It is rather awkward to convert the pneumatic signal into an electrical equivalent before putting the signal to use, and hence, a switch which can be directly operated by extremely small pressure changes is particularly useful.

In addition, it is further required that the switch of the type described, be light in weight, occupy little bulk, and be relatively inexpensive to manufacture.

In preferred form, the switch of this invention comprises a housing having a bore therein and a plunger member arranged to be movable axially within the bore. A flexible impervious diaphragm is placed over one end of the bore, the diaphragm having its intermediate portion doubled upon itself to form concentric cylindrical walls engaging the bore and plunger respectively so as to guide the plunger within the bore during displacement. At least one pair of flexible reeds are secured together at one end by conductive means, the free ends of said reed pair being fastened to said plunger member and to a fixed support respectively. A pair of conductive contact members each in circuit relation with an electrical source are arranged in the housing. The said one end of the reed pair describe an arcuate path upon displacement of the plunger, so that the touching of the said one end of the reed pair, with either one of said contact members, respectively completes an electrical circuit, whereby the magnitude of the displacement of the plunger determines which circuit is completed.

Accordingly, it is an object of this invention to provide an improved switch of the type described which is simple of construction, and easy to manufacture.

Another object is to provide a reliable switch which occupies a relatively small volume.

A further object is to provide an electrical switch of the type described which is adjustably responsive to changes in input pressure signals.

The novel features which are believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description when read in connection with the accompanying drawings in which:

Figure 1 is a front elevation in section of the switch in accordance with one illustrative embodiment of the invention;

Fig. 2 is a top plan view of the switch shown in Fig. 1 with the protective cover removed;

Fig. 3 is a sectional view taken along the line 33 in Fig. 1; and

"nited States Patent ice Fig. 4 is a side elevation of the switch shown in Fig. 1 with the protective cover removed in the interest of clarity.

Referring now to Fig. l of the drawing, spring housing is indicated generally at 10. A plunger guide plate member 12, internally bored at 14, is secured to housing 10 by means of a number of bolts 16, only one of which is shown on the drawing. The plunger, indicated generally at 18, comprises a rod portion 18a, an enlarged diameter portion 18b, and terminates in a plunger head which is arranged to fit in bore 19 of the housing 10 with a clearance. The housing 10 is adapted to receive a plunger spring 20, which bears against the portion 18b of the plunger. As may be seen from a study of Fig. 1, the portion 18b is resiliently urged against a shoulder in the housing. The bore 19 of the housing is sealed by means of a diaphragm or boot 22, which may be of rubber or other impervious flexible material; the boot 22 is held in position by means of an end plate 24, which is secured to the housing by means of four equally spaced bolts identified by the same number 26. The plate member 24 is centrally tapped at 28 so that it will receive a suitable pipe fitting. As may be seen in Fig. l, the enlarged diameter of bore 14 in plunger guide member 12 is fitted with a sleeve bearing 30 so that the plunger 18 may be easily displaced axially with a minimum of friction.

The diaphragm or boot 22 has its intermediate portion Next, the device is provided with a pair of reed mem-.

bers 32, 34. The reeds are secured at one end by means of a conductive button 36. The reed 32 is secured to the ends of plunger 18 by means of a contact block 38a and a cover member 38b of insulating material; the block 3811 is fitted over a reduced diameter portion of the plunger, the reed 32 being secured thereto by means of cover 38b and bolts 40. In like manner the other reed member 34 is also secured to a contact block 42a of in-. sulating material by means of cover member 425 and bolts 44 and 45. As will be seen from a study of Fig. 1, bolt 44 is recessed so that it is electrically isolated from bolt The reed members 32, 34 in the illustrated embodiment I are of unequal lengths, so that as the plunger 18 is displaced axially, the button 36 describes an arcuate path. As will be appreciated as the description proceeds, the reeds may be chosen in a variety of ways. Member 32, for example, may be of non-conductive material, since member 54 provides the requisite electrical path upon actuation of the switch. The reeds may have different spring constants, and may be of such selected materials as to be deformable in a predetermined non-- linear relationship, whereby to insure snap action and prevent an overrun as contact is made or broken.

The contact housing 48 will now be described; this unit contains and supports contact members 50 and 52. In this particular embodiment the members 50 and 52 are contact screws which are secured to the housing by means of screw bushings 56, 58; they may be adjusted in a direction at right angles to plunger travel to thereby vary. the magnitude of plunger. displacement required for. actuation ofthe associated electrical circuits. Asinay be observed from a study of the drawing, the axes. of members 50, 52 are displaced somewhatgthis is necessitated. by the fact that the conductive button 36 describes an arcuate and slightly upward path upon vertical movement of the plunger 18. The housing 48 is recessed at 54. to provide space for. movement of the reeds; the housing being fastened to the plunger guide member 12 and housing ltl'by meansof two bolts 60, 62. screwedv into tapped holes 61 and 63 respectively. The entire. switch may be mounted on a panel 64 in any convenient manner, such-.as by means of screws 65.

In order to protect the switchfrom dust and other deleterious influences, a cover. 66 issecuredlto the hens-- ing 48 by means of abolt 68 screwed into tapped hole-69.

Electrical connection to the switch is made. as follows: Wires 70 and 72. are secured to bushings 56 and 58 respectively. The housing 48 is recessed at 74. and 76 (Figs. 3, 4) and Wires 70, 72 are brought d'own.and

electrically secured to screw contacts 78, 80- whichare that within a predetermined tolerance range, the con ductive button 36 was on the midpoint of the. arcuate displacement path, and-not touching either contactmember 50 or 52. When a piece being gaged was. under'size, the pressure to the. plunger head 180 would fall off, causing the spring tov urge the plunger downward, with plunger part 18b being forced against the shoulder in housing 10. Button 36 was then forced into-electrical contact with member 52, and the circuit between terminals 78 and 45 was completed so as to cause a red light or other signal to be energized. When the contrary condition developed, and an oversizework piece was being gaged, the pressure would rise, displacing plunger 18 axially upwardand forcing button 36 into contact with member 50. The circuit would thus be completed between terminals 80 and 45, to energize a sig nal such as a green light for example, so as-to visually indicate an oversize condition. The operator may thus continuously gage a number of work pieces by pneumatic means, and the color of the signal lamp or the absence of either light beingilluminated, gives him the'required information concerning the dimensions of the pieces under test.

While specific embodiments have been shown and described, it will, of course, be understood that various other modifications may yet be devised by those skilled in the art which will embody the principles of the invention and found in the true spirit and scope thereof.

I claim:

l. A pressure switch comprising a housing having, a bore therein, a plunger movable axially within said.

In one. arrangement,

mounted adjustably in said housing in positions between which the joined ends of said reeds operate, whereby movement of said plunger will move said joined end of said reeds from one contact to the other.

2. A pressure switch comprising a housing having a bore therein, a plunger movable axially within said bore, a spring surrounding said plunger and forcing said plunger in one direction, a flexible impervious diaphragm closing one end of said bore, means to adjust fluid under pressure to one side of said diaphragm, said diaphragm having its intermediate portion doubled upon itself to form concentric cylindrical walls engaging said bore and plunger respectively to guide said plunger during its movement, a pair of flexible reeds, one reed having one end attached to said plunger, the second reed being fixed at one end to said housing, and the opposite ends of said reeds being attached together, an electrical connection for one of said reeds, and electrical contacts mounted adjustably in said housing, between which the joined ends of said reeds operate, whereby movement of said plunger will move said joined end of said reeds from one contact to the other.

3. A pressure responsive switch of the type described comprising a housing including a longitudinal bore therein, a plunger member displaceable axially within said bore, a diaphragm member sealing said bore in fluid-tight relation at one end'thereof, a source of fluid signals applied to the diaphragm member, at least one pair of reeds secured together at one end by conductive means, the free ends of said. reed pair being fastened to sai-d plunger member and to a fixed support respectively, a pair of conductive contact members each in circuit relation with an electrical source, the said one end of the reed pair describing an arcuate path upon displacement of the plunger, so that the touching 0f the said one end of the reed' pair with either one of said contact members, respectively completes an electrical circuit, whereby the magnitude of the displacement of the plunger determines which circuit'is completed.

4. Apressure switch according to claim 3 in which the diaphragm member comprises deformable material shaped so as to engage the end of'the plunger member, the boreside walls and the end face of the housing in contiguous relation.

5. A pressure switch according to claim 3 in which the said source offluid signals is a pneumatic gaging signal means.

6'. A pressure switch according to claim 3 in which the reed connected to the said plunger member is composed of non-conductive material.

7. A pressure switch according to claim 3 in which ment in a direction at right angles to the direction ofplunger displacement, whereby the magnitude of incremental pressure change required to complete the electrical-circuits may be initiallyvaried.

9. A pressure switch of the type described comprising,

a housing including a longitudinal bore therein, a diaphragm member. pneumatically sealing said bore at one end thereof, a pneumatic signal means applied to said diaphragm member, a plunger member adapted for axial displacement within said bore in response to incremental pressure changes, at.least a pair of conductive reeds secured together atone end, the free ends of said reed pair being fastened to said plunger member and to a fixed sup port respectively, a pair of conductive contact memberseach in circuit relation with an electrical source, mounted in spaced relation and. adjustable in a direction at right angles to the direction of plunger travel, the said-one end ofthe reed pair describing an arcuate path upon movement of the plunger, so that the touching of said one end of the reedpair with either one of said contact members, respectively completes an electrical circuit, whereby the predetermined magnitudes of the pneumatic pressure signals determine which circuit will be electrically completed.

10. A pressure switch according to claim 3 in which the reed members are of unequal lengths.

11. A pressure switch according to claim 9 in which the reed members are of unequal lengths.

12. A pressure responsive switch of the type described, comprising a plunger member displaceable axially, at least one pair of reeds secured together at one end by conductive means, the free ends of said reed pair being fastened to said plunger member and to a fixed support respectively, a pair of conductive contact members each in circuit relation with an electrical source, the said one end of the reed pair describing an arcuate path upon displacement of the plunger, so that the touching of the said one end of the reed pair with either one of said contact members, respectively completes an electrical circuit, whereby the magnitude of the displacement of the plunger determines which circuit is completed.

ReferencesCited in the file of this patent UNITED STATES PATENTS 889,212 De Barry June 2, 1908 908,679 Kelley Ian. 5, 1909 1,709,944 Loranger et al. Apr. 23, 1929 2,178,953 Chilton Nov. 7, 1939 2,435,143 Knauth Jan. 27, 1948 FOREIGN PATENTS 632,862 Great Britain Dec. 5, 1949 

